In article .com,
"Wimpie" wrote:

Hello Owen,

You are right, feeding in the middle is good, your feed line is in the
symmetry plane, where you have no E-field component parallel to your
feed line. The line itself will not distort the radiation pattern.

When it is a halve wave mono band antenna I would use a coaxial feeder
with balun (current mode balun with ferrite cores for example).

When the antenna has to work over multiple bands, you get problems with
the impedance when your dipole is a full wave. Matching the coaxial
feeder/balun combination will make almost sure all your power will be
wasted in the form of heat in the balun and or the coaxial feeder. In
that case I would prefer a symmetrical line (can have extremely low
loss) and a symmetrical tuner.

When one end of the dipole is close to ground or a large metal
structure, you may feed the dipole at that end as an alternative. When
your dipole is a multiple of halve a wavelength, the input impedance at
the ends is in the high kOhm range. So you will have a relative low
feed current and therefore also low ground current (so the ground can
be relatively bad).

I hope this and the other replies will help you to make good decision
on what to do.

Wim
PA3DJS.

yes thank you it will i appreciate everyones help it will allow me to
narrow down my guesses and know a bit better what to expect for sure

wish there was classes on this stuff


i dunno experimenting around with antennas is a lot of fun

ml

I know from various documents written by amateurs that there is a lot
of antenna related expertise within the Amateur Ccommunity (from which
I believe many are professionals). Many times it is difficult to
figure out who is telling "the facts".

Regarding classes, I am sure there are, but mostly are very expensive.
In the Netherlands there are a few companies that offer courses on
antenna design. Sometimes they are cancelled because of lack of
attendees.

With respect to books, many books tell you how to build an antenna from
a drawing (and not the theory behind it), other books tell you the
theory behind it, but require differential vector calculus.

It took me many years to understand antennas at the same level as my
electronic design activities.

Given all this, ¡I still like experimenting with antennas! I just
finished a design for the coming "Jamboree on the Air" to be held
during the weekend of 22 October (Scouting activity).

Best Regards,

Wim
PA3DJS

In article . com,
"Wimpie" wrote:

I know from various documents written by amateurs that there is a lot
of antenna related expertise within the Amateur Ccommunity (from which
I believe many are professionals). Many times it is difficult to
figure out who is telling "the facts".

Regarding classes, I am sure there are, but mostly are very expensive.
In the Netherlands there are a few companies that offer courses on
antenna design. Sometimes they are cancelled because of lack of
attendees.

With respect to books, many books tell you how to build an antenna from
a drawing (and not the theory behind it), other books tell you the
theory behind it, but require differential vector calculus.

It took me many years to understand antennas at the same level as my
electronic design activities.

Given all this, ¡I still like experimenting with antennas! I just
finished a design for the coming "Jamboree on the Air" to be held
during the weekend of 22 October (Scouting activity).

Best Regards,

Wim
PA3DJS

sounds like you are having fun, goodluck at the jamboree what type of
antenna did you design?

I live in nyc, and couldn't travel that far to take a class actually
my crazy dream was to have the class here around nyc and more
'practical' ham related going over different antenna topics (for ex)
from the simple/to advanced 'stuff' theory/design/actual etc

maybe a few other related topic's heck i cant even find any good
videos or classes to cover upgrading to Extra, i have the arrl book,
it's more of a test guide than a step by step too bad there wasn't
a instructor led upgrade to extra class around i'd pay up

i think i knew of a few places that used to give begginers training but
not sure if those same ones' are still around

my local ham store had test gear i used to be able to 'play with' but
they closed up long ago

i may be wrong statistically speaking but i think it's odd that the
states w/the highest ham population by far have the least ham radio
stores


ps my ex girlfriend was from freezland

thanks for all
ml

Hello,

Did you have a Dutch Girlfriend? Friesland is one of the northern
provinces of the Netherlands (The Frisian capital is Leeuwarden). I
live some kilometers north of Utrecht (in the middle of the
Netherlands).

Regarding the antenna for the JOTA. It is a simple center fed halve
wave double wire dipole (to increase useful bandwidth a bit) with
parallel ground wires (1.5m above ground) to reduce the losses in the
soil just below the antenna. The height above ground level will be
about 11m. According to simulation, the overall radiation efficiency
(ground losses included) will be about 80%, so we are not going to heat
the worms that much.

It has maximum radiation in a vertical direction. It will be used for
local (300km) traffic on 80 meters (Near Vertical Incidence Sky wave).
Just 2 days ago we received permission to use a sufficiently large open
area (with some domestic sheep) adjacent to the scout's building.

I had some ideas for other antennas (for 40m and 2m), but without
permission for using the adjacent land I don't want to spend time and
money.

The reason for an antenna optimized for local traffic is that most
scouts are a little bit nervous, they are not used to SSB quality sound
and their English is not that good for international contacts.

Best Regards,